The present invention relates to a cooling system for high-power internal combustion engines and, more particularly, to a cooling system for a diesel engine powered locomotive traction vehicle.
Cooling systems for internal combustion engines, such as the diesel engines used in locomotives, are known in the art for the purpose of maintaining engine and lubricating oil temperatures within desired operating ranges. Turbo-charged engines are also known to utilize cooling systems for conditioning the combustion inlet air after it is compressed in a turbo-charger. U.S. Pat. No. 5,415,147, incorporated by reference herein, describes a temperature regulating system for a turbocharged locomotive engine that is specifically designed to address the need for different cooling modes dependent upon changes in ambient air temperature and engine load. In one flow path taught in that patent, coolant heated by the engine is cooled by a primary radiator having a split outflow such that a portion may be further cooled in a subcooler. The coolant portion flowing through the subcooler is directed either to an engine intake air intercooler or back to a water reservoir. In a second flow path, heated coolant from the engine may be directed to the intercooler to heat the engine intake air.
The temperature regulating system of U.S. Pat. No. 5,145,147 defines three modes of operation as follows:
Mode 1: The entire hot coolant outflow from the engine is directed to the radiator/subcooler. Coolant passing through the subcoolers is used to cool the engine intake air in the intercooler. Mode 1 is used when coolant temperatures are highest, such as when the engine is at the highest power levels and/or when the highest ambient air temperatures are encountered. PA1 Mode 2: The radiator/subcooler are used to cool only a portion of the hot coolant outflow from the engine. The remainder is used to heat the engine intake air in the intercooler. Mode 2 is used when coolant temperature is high enough to warrant cooling but heating of the intake air is desired to obtain optimal engine operation. PA1 Mode 3: None of the coolant outflow from the engine is cooled in the radiator, but some of this heated coolant is used to heat the engine intake air in the intercooler. The radiator and subcooler are drained in this mode. Mode 3 is utilized when the heat demand on the engine is lowest, such as at low power loads and/or cold ambient air temperatures.
The particular flow paths for each of the three modes described above are disclosed in U.S. Pat. No. 5,415,147 along with the flow control system valving required to implement this cooling flow control system. The flow control system includes a two-position three-way "T-port" rotary valve shafted to an external air powered actuator (item 112 of the patent) and an associated on-off butterfly valve (item 206) for drainage of radiator inlet piping, and a second two-position three-way "L-port" valve shafted to an external air powered actuator (item 144) and its associated second on-off butterfly valve (item 168) for drainage of the subcooler outlet piping. Table 1 below illustrates the possible combinations of valve positions for the three way valves, with the flow ports of the valves designated as A, B and C. Three of the four combinations are used for implementing modes 1, 2, and 3 described above, and the fourth combination is unused in the prior art embodiments.
TABLE 1 Cooling System Mode vs Valve Position T T L L Mode 3-way 2-way 3-way 2-way Flow Path 3 C to B Open C to B Open Eng to W/T & I/C Rad & S/C to W/T 2 C to A Closed C to B Open Eng to Rad & I/C, S/C to W/T 1 C to A Closed A to B Closed Eng to Rad, S/C to I/C X C to B Open A to B Closed Not Used
The following abbreviations are used in Table 1: Eng for engine; W/T for water tank; I/C for intercooler; Rad for radiator; and S/C for subcooler.
Note that the fourth mode, indicated by Mode "X" in Table 1, is not used in the system described in U.S. Pat. No. 5,415,147, but is nonetheless available and may become "operational" due to a failure(s) in the valves.
The prior art system provides several operational advantages. However, it contains many valves and piping connections, thereby increasing the cost of manufacturing, the cost of operation, and the overall reliability of the system. Accordingly, it is an object of this invention to provide a cooling system for a turbo-charged internal combustion engine that provides all of the operational flexibility of the prior art system of U.S. Pat. No. 5,415,147 while being simpler and less expensive to construct and to operate. It is a further object of this invention to provide a cooling system and that is more reliable in its operation than prior art systems.